Hawai‘i and Pacific Islands

On large and small islands across the Pacific, climate variability and change threaten a range of resources, including fresh water supplies and coastal infrastructure. In the face of these challenges, people are taking steps to adapt to new conditions.

Key Points:

Warmer and drier conditions projected for the future mean that freshwater supplies will decrease on some Pacific Islands. Atolls and low-lying islands are especially vulnerable to freshwater shortages due to their small size and limited resources.

Rising temperatures and changing patterns of rainfall will stress native Pacific Island plant and animal populations and species. Combined with a range of non-climate stressors, these conditions increase the risk of local extinction for some species.

Higher ocean temperatures will increase coral bleaching, leading to changes in coral species composition, coral disease, coral death, and habitat loss. Increasing ocean acidification will have negative consequences for the entire marine ecosystem. Observed patterns in coastal and ocean fisheries will be altered due to changes in ocean circulation.

Mounting threats to food and water security, infrastructure, and public health and safety will lead to human migration from low islands to high islands and continental sites. Climate-related threats also make it difficult for indigenous communities to sustain their connection with defined places and their unique set of customs, beliefs, and languages.

The Pacific Islands region is spread across millions of square miles of the Pacific Ocean, encompassing more than 2,000 islands with about 1.9 million inhabitants, representing numerous languages and cultures. These islands attract millions of tourists every year and support a large U.S. military presence. The region includes diverse terrestrial and marine ecosystems, including pristine habitat that supports tremendous biodiversity.

This map show the locations of Hawai‘i and U.S.-Affiliated Pacific Islands, and highlights U.S. Exclusive Economic Zones and Marine National Monuments (MNM).

Across the Pacific Islands region, weather and climate are highly variable. Climate variability—best represented by the El Niño-Southern Oscillation (ENSO)—has a large influence on year-to-year changes in rainfall, sea level, and other climate variables across the islands. Several distinct multi-year patterns of shifting atmospheric pressures, wind patterns, and ocean temperatures can make it difficult to distinguish shorter-term climate variability from longer-term trends.

Despite the prevalence of short-term variations, several long-term trends have emerged from observations over the last century. Observed changes include an increase in average surface air temperature (most pronounced at high altitudes in Hawai‘i), a decrease in rainfall across much of the region, decreased groundwater storage in Hawai’i, rising mean sea level (especially in the western Pacific), more frequent and prolonged drought, changes in habitat and species distributions, rising ocean heat content, and changing ocean chemistry.

Adaptation is essential

Observed climate trends and results from global climate models make it clear that the cumulative impacts of climate change will require Pacific communities to implement some degree of climate adaptation in order to deal with new conditions. Informed and timely responses will be necessary, especially on low-lying islands and atolls, to improve communities’ resilience to the challenges posed by climate change. However, adaptive capacity across the Pacific Islands region varies with the availability of socioeconomic and institutional resources.

The Climate Resilience Toolkit offers case studies illustrating how people in the Pacific Islands are recognizing and addressing their climate threats.

Additional research, continued monitoring, a sustained assessment process, and public engagement in the development and sharing of useful information will enhance Pacific Islanders’ ability to address climate challenges. Island residents can participate in and/or learn from regional coordination efforts that facilitate data collection, analysis, and access to information: these efforts offer significant contributions for groups who are developing adaptation plans and policies. Regional communication and collaboration provides a strong foundation for ongoing efforts to build resilience in the face of challenges from a changing climate.